STORY HIGHLIGHTS
Blizzard warnings are in place in 7 states The mayor of St. Louis among the thousands of stranded travelers, an official says Snowfall could reach a rate of 2 to 3 inches per hour in Chicago - Subzero temperatures are forecast across the upper Plains and Midwest
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(CNN) -- Oklahoma was under a state of emergency and 600 National Guard troops were mobilized in Missouri as the Plains and the Midwest braced Tuesday to take the brunt of powerful winter storm system.
The National Weather Service forecast blizzard conditions across portions of seven states, from Oklahoma to Illinois, Wisconsin and Indiana. Winds gusts of up to 40 mph are expected.
Emergency personnel in Oklahoma City, St. Louis and Chicago, among other locales, vowed they were prepared to weather the storm. The leaders of several states, many of which have already had a difficult winter, also commandeered their forces even as they urged people to stay home.
"Folks should batten down the hatches and hold on," Missouri Gov. Jay Nixon said. "The most likely place to get hurt is out on the road."
Teeth-chattering cold will filter in behind the system, plunging temperatures to subzero in the upper Plains states.
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The expansive storm will ultimately affect about three-quarters of the United States. The weather service has posted winter storm warnings, watches or advisories in some 30 states.
Heavy snow is predicted along a sweeping 1,500-mile arch, starting in central Texas and ending in Connecticut.
Along with its strength, the system's immense size sets it apart -- spanning more than 2,100 miles from southwestern Arizona to central Maine.
"A storm of this size and scope needs to be taken seriously," said Craig Fugate, administrator of the Federal Emergency Management Agency.
Still, some of the biggest concerns Tuesday were in cities like Chicago.
"Combined snow totals ... through Wednesday may exceed a foot and a half across much of northern Illinois and far northwest Indiana," the weather service said.
"This storm could be one of the top 10 biggest snowstorms ever in the city," said CNN meteorologist Sean Morris.
According to the National Weather Service, snowstorms that drop over 15 inches of snow occur about once every 19 years in Chicago. The last time this happened was in January 1999, when 21.6 inches of snow was recorded in the city.
Officials have added 120 garbage trucks with specially attached snow plows to the city's fleet of 274 trucks in expectation of heavy snowfall, said Jose A. Santiago, executive director of the city's Office of Emergency Management.
Snowfall could reach a rate of 2 to 3 inches per hour with northeasterly winds of 25 mph to 40 mph, creating dangerous "white-out" conditions across the entire Chicago metropolitan area, the weather service reported.
Blizzard or near blizzard conditions are expected as far south as Oklahoma City on Tuesday, where snow accumulations there will be measured in feet, not in inches.
Oklahoma's governor, Mary Fallin, released a statement on Monday declaring a state of emergency for all 77 counties in the state.
"This disaster declaration will make sure we can prepare for the winter weather ahead of the storm," Fallin said. "We encourage all Oklahomans to prepare for the storm before it arrives."
The mayor of Oklahoma City told residents to stay off the streets. Mick Cornett noted that most city and state government offices would be closed Tuesday and asked that local businesses do their best to keep their employees home as well.
Oklahoma City officials urged residents to make early provisions -- such as stocking up on water, batteries, medications and canned foods in case power outages occur. The storm is expected to have snowfall rates of up to 3 inches per hour, according to the weather service.
"We're not strangers to weather," said Michelann Ooten with Oklahoma City's emergency management operations. "We've been working on this since last week."
Ooten said her office had already contacted FEMA to secure generators and supplies in case emergency shelters are needed.
St. Louis Mayor Francis Slay tried to cut short a trip to New Mexico to head home in time for the storm, only to have his flight canceled due to the weather, his chief of staff Jeff Rainford said.
"So he's one of the (thousands) stranded as well," said Rainford.
Other cities likely to be affected during the week include Milwaukee, Cleveland, Providence in Rhode Island and the New York cities of Buffalo, Syracuse and Albany.
Heavy snowfall won't be the only hazard from this major storm system. The subfreezing temperatures could coat trees, power lines and roads in ice from Missouri to southern Illinois and eastward into central Indiana, forecasters said.
Ice accumulations of up to three-quarters of an inch will be possible, and they are likely to combine with gusty winds to cause tree branches to fall on power lines, according to forecasters.
With temperatures expected to drop well below zero by Wednesday, parts of the Texas Panhandle and western Oklahoma will experience some of the coldest air this season, Morris said.
Strong winds will combine with the cold temperatures to create extremely dangerous wind chills, according to forecasts.
But the storm's wrath won't end there.
Severe thunderstorms are likely to develop along a trailing cold front from a main low-pressure area. That sets up a significant potential for tornadoes in Arkansas, Louisiana, Mississippi, Tennessee and Alabama.
The winter weather is prompting airlines to cancel flights by the hundreds and numerous carriers are letting customers make changes to their itineraries without the typical fees.
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